1. Field of the Invention
The present invention relates generally to the field of electrical connectors and connection apparatus, and particularly in one aspect to an electrical connector apparatus useful in, inter alia, biomedical applications.
2. Description of Related Technology
In certain electrical connector applications, multiple (often competing) design and performance requirements exist, thereby significantly constraining the selection of connector technology for use in that application. This is especially true of certain clinical or biomedical applications such as impedance cardiography (ICG) and electrocardiography (ECG), wherein it is highly desirable to have a connector which is low cost, clinically rugged and robust, yet which provides both acceptable electrical performance (including low impedance) in a stable and repeatable manner. ICG and ECG connector assemblies have been historically characterized by high cost and substantial complexity of design. Unfortunately, such high cost tends to steer the clinician (or medical facility) using the connector to use the connector in an unintended manner. For example, a clinician may attempt to use a single connector for both ECG and ICG measurements. Such uses however do not produce ideal results and create significant barriers to adoption of the technology in the first place.
Ensuring a clinician employs a correct ICG or ECG connector assembly for a particular sensor is also crucial when the clinician utilizes methods which include the simultaneous operation of ECG and ICG. One exemplary method requiring simultaneous operation of ECG and ICG is described in co-owned U.S. Pat. No. 7,270,580 issued Sep. 18, 2007 and entitled “Methods and Apparatus for Conducting Electrical Current”, which is incorporated by reference in its entirety. As disclosed therein, an electrode having at least two sensors of differing size disposed thereon is used; at least one of the sensors is adapted to be operated with an ICG connector assembly and the other for an ECG connector assembly. The electrode enables clinicians to apply ICG methods to measure a stroke volume, which is then multiplied by heart rate measurements obtained by ECG methods to obtain a cardiac output measurement.
Generally, in ICG applications sensors are disposed on the neck and chest of a patient to transmit and detect electrical and impedance changes in the thorax. The impedance measurements are then used to measure and calculate hemodynamic parameters. As indicated, one sensor is used for transmitting electrical current through the chest, while the other is used to detect or sense voltage. The sensors comprise at least two different sizes to facilitate coupling of connectors to the sensors in the correct orientation. In other words, the different sized sensors prevent connectors (and electric components associated therewith) from being inadvertently coupled to the wrong sensor. Accordingly, exemplary ICG connectors would be very simple in construction and low in cost, yet unique to the particular ICG sensor that it belongs (e.g., either the current source or the voltage sensor). Thereby providing accurate measurements and prevent misuse, including misuse of ICG connectors for ECG sensors.
Another consideration especially for biomedical applications relates to so-called “pull away” force. In accordance with standards set forth in by the American National Standards Institute (ANSI) and Association for the Advancement of Medical Instruments (AAMI) for ECG cables and electrical wires (ANSI/AAMI EC 53-1995 ECG Cables and Lead Wires Standard), which is incorporated herein by reference in its entirety, an ECG connector must be adapted to break free or pull away at a certain force (e.g., when the ECG equipment and the patient having sensors and a connector mounted on are pulled away from one another). The standard defines that when such an event occurs, the connector and its cables break away from the sensors disposed on the patient and do not remain hanging from the sensors on the patient, but rather are adapted to detach as a unit from the sensors. This requirement is intended to maintain the electrical safety of the patients and clinicians; e.g., so that the free ends of the leads can not be inadvertently or intentionally plugged into another piece or equipment or otherwise present an electrical shock or grounding hazard. Hence, a connector for use in such applications must be designed so as to provide the requisite electrical contact and low-impedance interface, be rugged and positive in its mating, yet pull off the sensor (terminal) at a force below that which would cause the cables to be dissociated from the parent ECG equipment.
A great variety of different electrical connector designs (biomedical and otherwise) are known in the prior art, the following being generally representative.
U.S. Pat. No. 1,212,821 to Schade discloses a device for spring fastening a wire device to an electrical conductor.
U.S. Pat. No. 2,758,947 to Feighner discloses a method of clamping a spring loaded clip onto wires, terminals or other electrical conductors.
French Patent No. 964,611 to Ford issued August 1950 discloses a metallic loop element with aperture adapted for mating with a spark plug electrode. The loop is expanded by biasing two portions of the loop toward one another.
U.S. Pat. No. 3,774,143 to Lopin discloses an adapter for use in making an electrical connection between an electrode and a cable connected to a monitoring instrument.
U.S. Pat. No. 4,040,697 to Ramsay, et al. issued Aug. 9, 1977 entitled “Electrical connector” discloses an electrical connector that has a resilient, stamped, metallic leaf contact defining a narrow neck contact entrance area and having reversely bent ends on either side of said area. A plastic body section embeds the ends and spans the area to provide two side by side lever legs arranged to act so that pressure on the legs resiliently opens the narrow neck to allow entrance of a second body contact. Relaxation of pressure on the legs causes resilient action of the connector to provide gripping of the second contact with a positive three point grip.
U.S. Pat. No. 4,178,052 to Ekbom, et al. issued Dec. 11, 1979 entitled “Medical terminal clip member for attachment to patient electrodes” discloses a medical terminal clip that has a body member with a longitudinal axis and a pair of laterally spaced leg members extending in approximately the longitudinal direction and pivotally connected for relative movement. The respective spaced leg members form a variably spaced electrode receptacle on one side of the pivotal connection. A beryllium copper conductive member is embedded in the body member and is formed from a strip of metal bent into approximately an M-shape with side flanges on the leg members to ostensibly provide additional strength. A shield or barrier member extends at least between the approximate ends of the leg members on the other side of the pivotal connection while permitting relative movement of the leg members. The shield member is designed to close longitudinal access to the space between the leg members and thereby prevent any dislocation of the terminal clip member by catching onto exterior objects such as other terminal wires.
U.S. Pat. No. 4,206,960 to Tantillo, et al. issued Jun. 10, 1980 entitled “Electrical connector” discloses an electrical connector for engaging a terminal stud that has first and second insulating spring arms each carrying a conductive metal contact with the metal contacts defining through holes for electrically contacting a shank of a terminal stud. The metal contacts normally are in opposed spaced relationship to each other but are superimposed over each other and resiliently biased to their original position when the spring arms are squeezed toward each other by finger pressure. Release of the pressure causes the contacts to grasp the shank of a terminal stud over which the contacts are positioned. An electrical connector is formed by positioning a preformed end piece over an insulated wire and then molding a plastic connector end in abutting relationship with at least a portion of said preform whereby the molding and forming temperature used does not adversely affect the insulation of said wire.
U.S. Pat. No. 4,220,387 to Biche, et al. issued Sep. 2, 1980 entitled “Medical clip” discloses a medical terminal, particularly for use in connecting a lead wire or conductor to an electrode conventionally secured to the skin surface of a human or animal. The electrode comprises a male projection of the buttontype with an enlarged diameter head portion disposed within a recessed area of the electrode. The clip is generally V or wishbone shaped and includes a pair of support arms secured together at one end and normally spaced from each other at the other end. The arms carry resilient conductive loops normally biased out of overlapping condition but movable upon the application of external force into an overlapped condition wherein the clip may be applied over the head portion of the electrode. The support arms have offset depending shoulder portions from which the conductive loops extend and which are positionable within the recessed area of the electrode when the arms are moved toward each other. The support arms are integrally formed of resilient dielectric plastic material in an initial unstressed generally V-shape, with a female socket embedded in the plastic and electrically connected by conductor means to the conductive loops. Replaceable or interchangeable identification means is removably mounted on the clip in the area of the female socket, and a strain relief cover is removably positionable on the clip over said female socket and over said identification means to provide strain relief for the connection to a lead wire, and the cover is at least in part transparent to provide visual observation of the identification means.
U.S. Pat. No. 4,671,591 to Archer issued Jun. 9, 1987 entitled “Electrical connector” discloses a connector for establishing electrical connection between a conductor and a patient engaging electrode that includes a conductive post extending from the electrode. The post has a proximal portion, a distal portion, and an intermediate portion having a diameter smaller than the diameter of the distal portion. The connector comprises insulation means shaped to form a socket open at one end, a pair of first spring members, a pair of second spring members, and means for electrically connecting the conductor to the second spring members. The first spring members are laterally positioned with respect to one another in the socket, and the second spring members are laterally positioned with respect to one another in the socket closer to said one end than the first spring members. The first and second spring members are positioned and constructed such that when the post is inserted in the socket, the second spring members grip the proximal portion of the post, and the first spring members and the intermediate and distal portions of the post comprise a detent mechanism that resists removal of the post from the socket.
U.S. Pat. No. 5,277,613 to Neward issued Jan. 11, 1994 entitled “Electrode junction assembly” discloses an electrical junction block particularly for use with a fetal electrode and electronic monitor. The junction block comprises a housing having a cavity therein, and a substantially U-shaped spring disposed in the cavity. The spring has legs which are biased outwardly by a suitable coil spring. The housing contains electrical contacts and wires connected thereto, and the U-shaped spring can be depressed to provide openings for receiving electrode wires. A mounting pad can be disposed on the housing for facilitating mounting of the assembly on a person during use.
U.S. Pat. No. 5,895,298 to Faupel, et al. issued Apr. 20, 1999 entitled “DC biopotential electrode connector and connector condition sensor” discloses an electrode connector and connector condition sensor for a biopotential sensing apparatus. A plurality of electrodes are connected to individual output leads for individual electrode channels by a connector which does not abrade the surface of the electrode button contact and does not require that pressure be applied to the electrode during connection. Two spring biased conductive arms for the connector are spread apart by the cam surface of an actuator button to receive the button contact and are contoured to engage substantially the peripheral surface of the button contact when the actuator button is released. The biopotential sensing apparatus includes a processor which senses the loss of signal in any electrode channel during a test period and activates an indicator to provide a warning indication.
U.S. Pat. No. 6,142,949 to Ubby issued Nov. 7, 2000 entitled “Lead protection and identification system” discloses a lead protection and identification system for a medical diagnostic device. Electrodes are placed on predetermined locations of a patient, and the system includes clips for attaching to the electrodes. The system identifies a lead and provides information to a user as to which one of the electrodes the lead should be connected to. Potentially dangerous signals are prevented from being inputted to a clip when the clip is not connected to an electrode and prevents the patient from being injured.
United States Patent Publication No. 20030068914 to Merry, et al. published Apr. 10, 2003 entitled “Precordial electrocardiogram electrode connector” discloses an electrocardiogram electrode connector for connecting an electrode to an electrocardiogram device. The connector of the present invention comprises a lower portion having an electrode end and an ECG end, and an upper portion pivotally connected to the lower portion. The upper portion likewise has an electrode end and an ECG end. The connector also comprises a spring between the lower portion and the upper portion to bias the electrode ends together to clamp about an electrode. Further, the connector comprises an electrical assembly having an elastomeric electrical connector to provide electrical continuity between the electrode and the ECG device when the electrode ends of the lower portion and the upper portion of the connector are biased together.
United States Patent Publication No. 20040039275 to Sato, et al. published Feb. 26, 2004 entitled “Biological electrode and connector for the same” discloses a conductive member adapted to be attached onto a living tissue to detect a bioelectrical signal. A retainer retains the conductive member on the living tissue. A lead member is partly brought into contact with the conductive member to lead out the bioelectrical signal to a connector. A waterproof sheet covers the lead member in a watertight manner, while exposing a portion of the lead member from which the biological signal is led out.
United States Patent Publication No. 20040072475 to Istvan published Apr. 15, 2004 entitled “Electrode connector” discloses an electrode connector for connecting a conventional tab electrode or sensor to a lead assembly for use with a physiological data collection system. The electrode connector includes a lead connecting portion for attaching the electrode connector to a lead assembly and a tab connection portion for attaching the electrode connector to a tab electrode or sensor. During use, the electrical signals corresponding to physiological data of the patient pass from the tab electrode or sensor, through the electrode connector, and to the lead assembly.
United States Patent Publication No. 20040106964 to Fischer, et al. published Jun. 3, 2004 entitled “Implantable Medical Device with Multiple Electrode Lead and Connector with Central Fastener” discloses an implantable medical device such as a cardiac stimulator, a multi-electrode lead attached to the device, and a connector coupling the device to the lead. The lead has multiple electrodes, each electrode connected to a wire extending though the lead. The electrodes may be circumferential coils or rings, for example. The lead has a connector that fits into a recess on a surface of the device or apparatus. A bottom wall of the recess has an array of apparatus connections deployed around a threaded bore. The connector is attached to the apparatus by a screw with a threaded shaft and an enlarged head. The screw passes through a central bore in the connector. Electrical connections form a regular pattern, such as a rectangular or square grid, or a radial pattern, around the central bore. A pair of O-rings or seals surround the connections. A gasket, mounted on male connections or contacts, fits around female connections that may be on either the apparatus or the connector.
Despite this broad variety of designs, what is needed is a connector which is inter alia uniquely adapted to the sensor or terminal it is to be used with so that the chances of using the connector and/or the terminal improperly are mitigated. An exemplary connector would also ideally be easy to use and provide optimal surface area contact between the sensor and connector. Likewise, the connector would substantially frustrate modification of the connector in order to provide connection to unintended sensors.
Further, an ideal connector would be adaptable to exhibit desired “pull-away” properties.